I am wondering why you would expect and want more from GM vintage services. If the original build sheet that came with the car when new cannot be had, the GM docs that are available today is as good as it gets. It sounds like you are worried the vin # for this car has been circulated and you suspect a car has been created from the available paperwork. If thats the case,then for my money anyways,I would seek Jerrys help to try and determine exactly what the car is. Go through the process and don't take any shortcuts. If its important do it right.